Final answer:
option c,A router is the device that enables communication between different subnets by operating at the network layer of the OSI model. It uses IP addresses to route data packets to the correct destination.
Step-by-step explanation:
To enable communication between subnet 1, subnet 2, and subnet 3, the device that operates at the network layer of the OSI model is a router. A router is designed to forward data packets between different networks, and it uses IP addresses to make decisions about where to send the packets. Hub, Switch, and Bridge operate at different layers of the OSI model. A hub operates at the physical layer and simply repeats signals to all ports. A switch operates at the data link layer and forwards frames within the same network. A bridge is also used at the data link layer to segment a network or extend a network by forwarding frames between two LANs.
The device that operates at the network layer of the OSI model to enable communication between these three subnets is a router. A router is a networking device that forwards data packets between networks. It examines the header information of each packet and determines the most efficient path for the data to reach its destination.